Diabetic retinopathy is clinically defined as a disease of the retinal microvasculature, and most research on its pathogenesis to date has focused on molecular and metabolic defects within the blood vessel cells themselves. In recent years, we have provided evidence that cells in the outer retina play a critical role the development of diabetic retinopathy. The current application will investigate the hypothesis that visual cycle activity plays a key role in initiation of the degenerative vascular lesions in early stages of diabetic retinopathy, and does this by increasing oxidative stress and inflammation within rod photoreceptors. Ultimately, the stressed photoreceptors release soluble factors (including cytokines) that damage the vasculature secondary to activating circulation leukocytes. Thus, the central hypothesis of our proposal is that hyperglycemia or other abnormalities that stress photoreceptors (such as rhodopsin mutants) lead to generation superoxide and other reactive products, and that these abnormalities initiate the structural and functional changes of the microvasculature which are clinically recognized as early diabetic retinopathy. Specific Aims will be: (1) to evaluate the roles of visual cycle activity in the retinal capillary damage caused by diabetes., (2) to investigate the roles of oxidative stress and/or inflammation within photoreceptors to initiate damage to the retinal vasculature, and (3) to identify soluble factors released by photoreceptors in diabetes, and mechanism by which those factors contribute to retinal capillary damage. The research proposed in Aim 1 will use mouse models in which RPE65 and LRAT are deficient, as well as a novel inhibitor of RPE65 to assess visual cycle activity. Aim 2 will be tested using mice having (i) photoreceptor-specific knockdown of activities of NADPH oxidase activity and NF-?B activation. Diabetes will be induced experimentally in male and female mice. This is a highly novel and testable hypothesis that will be conducted by an experienced research team. Confirmation of retinal photoreceptor cells as contributors to retinal capillary disease in DR (and other retinal vascular diseases) will offer several novel approaches to inhibit the development of these retinopathies.